It was a place of silence, forced learning and fear. It was called a “transformation centre” hidden in the mountains of far western China, bereft of any obvious sign indicating its purpose. But it looked and felt like a jail.

For months, Sayragul Sauytbay worked inside, teaching Mandarin and propaganda to Muslim detainees swept up in a broad Chinese campaign to eradicate what Beijing calls extremism.

Then, facing internment herself, she fled to neighbouring Kazakhstan – where she was arrested after China sought her deportation. But her lawyers argued that she could face torture if returned, and on Wednesday, a Kazakh court declined to send her back, giving her a six-month suspended sentence.

In freeing Ms. Sauytbay, an ethnic Kazakh, Kazakhstan rebuffed a powerful neighbour and allowed her to become the first instructor to publicly describe her experience in the re-education system. Her account buttresses the growing body of evidence about an extensive network of internment facilities that activists and some scholars have likened to military prisons. Chinese officials have not confirmed their existence.

Ms. Sauytbay’s willingness to speak has earned her plaudits in Kazakhstan, though it has come at a personal cost: Shortly after her she walked out of court Wednesday, her sister and two friends still living in China were taken away. She believes it was retaliation for releasing information about re-education centres that China treats as a state secret.

”Yesterday at 6 p.m. I was released and saw my kids. I felt very good at that moment,” she told the Globe and Mail in an interview Thursday afternoon, minutes after confirming that the three people had vanished. “But this happiness failed to last 24 hours.”

A primary school teacher who became a kindergarten administrator, Ms. Sauytbay was ordered last November to work in a new place. “They said I must go. I think if I refused them, I would have ended up being locked in that re-education centre as well,” she said.

She had been chosen to teach inside the internment camp​ because she could speak both Kazakh and fluent Mandarin. Often, she was driven to work at night, to a distant place in the mountains of Zhaosu County, on the far western border between China and Kazakhstan. The facility was surrounded by high walls and barbed wire. It looked “very, very scary. Just one glimpse would frighten you,” she said.

Inside were roughly 2,500 people, all of them Muslim, most of them ethnic Kazakhs. None were Han Chinese, the dominant group in China. “They were all ethnic minorities,” she said, ranging in age from their upper teens to their 70s.

She received no explanation for why they were there, nor the purpose of the instruction she was ordered to deliver.

“They told us nothing,” she said. “Even as a teacher, the knowledge we had about that place was very limited. They had many of their own highly confidential secrets.”

Work in the camp had no fixed schedule, each day a mix of teaching and “special tasks.” The latter might be training students to sing the Chinese national anthem, or Communist standbys such as “Without the Communist Party, There Would Be No New China.”

Mostly, though, she was told to teach Mandarin. “We had to do many mentally oppressive and cruel things,” she said. Her superiors would “set a goal for us to fulfill and we needed to force them to learn.” That included septuagenarians made to maintain the prescribed pace. “If the person refused to learn, he would be threatened,” she said.

The instruction resembled education, but she could discern no benefit. “All it brings is pain, scars and pressure,” she said. The re-education centre was a cauldron of stress. “When you eat, sleep, use the bathroom – all your behaviours are carefully monitored. That’s where the mental pressure comes from. I still feel pain when I think about it. There’s no freedom,” she said.

“People didn’t dare to speak even a single word out loud. Everyone was silent, endlessly mute, because we were all afraid of accidentally saying something wrong.”

She did not personally see violence, although she did see hunger. Detainees had only three kinds of food: rice soup, vegetable soup and nan bread. “There was no meat. There was never enough to eat. People were malnourished,” Ms. Sauytbay said.

In her time there, she was not aware of any detainees being released.

After four months at the centre, she returned to her kindergarten class. But a week later, she was removed from her position. Her husband and children had secured citizenship in Kazakhstan. That was enough to place her under suspicion.

She was told “I deserved punishment. They said I would have to give up my job and be sent to a re-education centre for one to three years.”

Instead, she fled to Kazakhstan where “she’s regarded as a hero by many people in this country,” said Kayrat Jawhax, a Chinese-Kazakh activist.

“She is the only person who has worked in a re-education camp and come out of there alive. She knows more about the camps and criminal actions of the Chinese government.”

Ms. Sauytbay said she was merely following her conscience.

“If a person breaks the law, he should receive legal punishment. Why re-education?” she said. “It is too cruel. My attitude will never change. This whole thing is unacceptable.”